Lecture Outlines Chapter 11 Astronomy Today 8th Edition Chaisson/McMillan
Chapter 11 Jupiter
Units of Chapter 11 11.1 Orbital and Physical Properties 11.2 Jupiter s Atmosphere Discovery 11.1 A Cometary Impact 11.3 Internal Structure Discovery 11.2 Almost a Star? 11.4 Jupiter s Magnetosphere 11.5 The Moons of Jupiter 11.6 Jupiter s Ring
11.1 Orbital and Physical Properties This figure shows the solar system from a vantage point that emphasizes the relationship of the jovian planets to the rest of the system
11.1 Orbital and Physical Properties Three views of Jupiter: From a small telescope on Earth; from the Hubble Space Telescope; and from the Cassini spacecraft
11.1 Orbital and Physical Properties Mass: 1.9 10 27 kg (twice as much as all other planets put together) Radius: 71,500 km (11.2 times Earth s) Density: 1300 kg/m 3 cannot be rocky or metallic as inner planets are Rotation rate: Problematic, as Jupiter has no solid surface; different parts of atmosphere rotate at different rates From magnetic field, rotation period is 9 hr, 55 min
11.2 Jupiter s Atmosphere Major visible features: Bands of clouds; Great Red Spot
11.2 Jupiter s Atmosphere Atmosphere has bright zones and dark belts Zones are cooler, and are higher than belts Stable flow, called zonal flow, underlies zones and bands Simplified model
11.2 Jupiter s Atmosphere Real picture is much more complicated Here: Wind speed with respect to internal rotation rate
11.2 Jupiter s Atmosphere Composition of atmosphere: mostly molecular hydrogen and helium; small amounts of methane, ammonia, and water vapor These cannot account for color; probably due to complex chemical interactions
11.2 Jupiter s Atmosphere No solid surface; take top of troposphere to be at 0 km Lowest cloud layer cannot be seen by optical telescopes Measurements by Galileo probe show high wind speeds even at great depth probably due to heating from planet, not from Sun
11.2 Jupiter s Atmosphere Great Red Spot has existed for at least 300 years, possibly much longer Color and energy source still not understood
11.2 Jupiter s Atmosphere Lightning-like flashes have been seen; also shorterlived rotating storms One example: Brown Oval, really a large gap in clouds
11.2 Jupiter s Atmosphere Here, three white storms were observed to merge into a single storm, which then turned red. This may provide some clues to the dynamics behind Jupiter s cloud movements.
Discovery 11-1: A Cometary Impact July 1994: Comet Shoemaker-Levy 9, in fragments, struck Jupiter, providing valuable information about cometary impacts
11.3 Internal Structure We find that Jupiter radiates more energy than it receives from the Sun: Its core is still cooling off from heating during gravitational compression. Could Jupiter have been a star? No; it is far too cool and too small for that. It would need to be about 80 times more massive to be even a very faint star.
11.3 Internal Structure No direct information is available about Jupiter s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is a rocky core.
Discovery 11-2: Almost a Star? Jupiter is much too small to have become a star needs 80 times more mass! But its energy output was larger in the past; could have been 100 times brighter than the Moon as seen from Earth Dwarf star in Jupiter s place probably would have made stable planetary orbits impossible Jupiter played invaluable role in sweeping solar system clear of debris before too much reached Earth otherwise life on Earth might not have been possible
11.4 Jupiter s Magnetosphere Jupiter is surrounded by belts of charged particles, much like the Van Allen belts but vastly larger Magnetosphere is 30 million km across
11.4 Jupiter s Magnetosphere Intrinsic field strength is 20,000 times that of Earth Magnetosphere can extend beyond the orbit of Saturn
11.5 The Moons of Jupiter 63 moons have now been found orbiting Jupiter, but most are very small The four largest are the Galilean moons, so called because they were first observed by Galileo: Io, Europa, Ganymede, Callisto Galilean moons have similarities to terrestrial planets: orbits have low eccentricity, largest is somewhat larger than Mercury, and density decreases as distance from Jupiter increases
11.5 The Moons of Jupiter Jupiter with Io and Europa. Note the relative sizes!
11.5 The Moons of Jupiter Interiors of the Galilean moons
11.5 The Moons of Jupiter Io is the densest of Jupiter s moons, and the most geologically active object in the solar system: Many active volcanoes, some quite large Can change surface features in a few weeks No craters; they fill in too fast Io has the youngest surface of any solar system object
11.5 The Moons of Jupiter Orange color is probably from sulfur compounds in the ejecta
11.5 The Moons of Jupiter Cause of volcanism: Gravity! Io is very close to Jupiter and also experiences gravitational forces from Europa. The tidal forces are huge and provide the energy for the volcanoes.
11.5 The Moons of Jupiter Volcanic eruptions also eject charged particles; these interact with Jupiter s magnetosphere and form a plasma torus
11.5 The Moons of Jupiter Europa has no craters; surface is water ice, possibly with liquid water below Tidal forces stress and crack ice; water flows, keeping surface relatively flat
11.5 The Moons of Jupiter Ganymede is the largest moon in the solar system larger than Pluto and Mercury History similar to Earth s Moon, but water ice instead of lunar rock
11.5 The Moons of Jupiter Callisto is similar to Ganymede; no evidence of plate activity
11.6 Jupiter s Ring Jupiter has been found to have a small, thin ring
Summary of Chapter 11 Jupiter is the largest planet in the solar system Rotates rapidly Cloud cover has three main layers, forms zone and band pattern Great Red Spot is a very stable storm Pressure and density of atmosphere increase with depth; atmosphere becomes liquid and then metallic
Summary of Chapter 11 (cont.) Relatively small rocky core (but still about 10x size of Earth) Still radiating energy from original formation 63 moons, four very large Io: active volcanoes, due to tidal forces Europa: cracked, icy surface; may be liquid water underneath Ganymede and Callisto: similar; rock and ice